Even if the supply voltage is 5V the output For other led colors the forward voltage will The forward voltage can vary between 2V and 2.6V for a red led. If VCC is 5V and the forward voltage for a red led is 2V then: Subtract the LED forward voltage from VCC and divide by the desired current. Sizing the resistors for an individual segment is the same as for any LED. Even at 14mA and multiplexed the display will be very bright.Ĭhoosing the current limiting resistors for a 7 segment display Microcontroller pin can output maximum 20mA so the resistors are calculatedįor 20mA. The datasheet saysĢ5mA continuous current and even 90mA when they are multiplexed but a single Since each segment is an LED it can draw 20mA of current. If you are going to use this library it is important that all pins that areĬonnected to A through G segments to be on the same port. So for 2 digit display we will need 8 + 2 The display has the number of necessary pins will be the same only the pinsįor selecting the digits will vary. OPD-Q5621LE-BW - a 4 digit common cathode displayĨ pins of the microcontroller are used to control the 7 segments and the dotĪnd another 4 pins to select the active digit. A, B, C, D, E and F is 0.Ĭonnecting a common cathode 4 digit 7-segment display to a microcontroller Turning on only some specific segments, any numbers, minus sign or someĪlphabetical characters can be displayed. Note that, the Pins 3 and 8, which are named COM are connected internally and, in this case, they are the common anode Pins (+5V).By convention each segment is labeled from A to G as in the image above. The following image shows the Common Anode 7 Segment Display Pinout. The difference is actually very small, which you will see. Let us now see the 7 Segment Display Pinout for both Common Anode as well as Common Cathode types. We will see more about this when we see the 7 Segment Display Pinout for both common anode and common cathode types. In case of Common Cathode 7 Segment Display, we connect the common cathode pin to GND (i.e., negative of the power supply) all the time and make a particular anode pin HIGH to turn ON the corresponding segment. To turn ON a particular segment, we make the corresponding cathode pin LOW. In case of Common Anode 7 Segment Display, we connect the common anode pin to V CC (i.e., positive of the power supply, usually +5V) all the time. There is one important thing about common anode and common cathode type 7 Segment Displays that you need to remember. All the cathode terminals of the 8 LEDs are connected together and made common. The following image shows the internal connection of a Common Anode type 7 Segment Display.Ĭoming to the Common Cathode type 7 Segment Display, you guessed it right, the connection is just the opposite. As a result, we have just 9 pins/connections to control the entire 7 Segment Display unit (8 Cathode pins of 8 LEDs and one common Anode pin). In a Common Anode type 7 Segment Display, the anodes of all the 8 LEDs are connected together and made common for the entire display unit. They are Common Anode and Common Cathode. But what about its internal circuitry and components? As each segment in a 7 Segment Display is nothing but an LED, the internal circuit and components are nothing but a bunch of LEDs connected in a special pattern (an additional LED for the dot).īased on the internal connection of the LEDs, we have two basic types of 7 Segment Displays. Till now, we have spoken only about the output of the 7 Segment Display. You can see how numbers from ‘0’ through ‘9’ will look on a typical 7 Segment Display in the following image. For example, to display the number ‘0’, all the segments must be ON except the segment ‘G’.

To display a particular number, you have to turn ON or OFF a group of Segments. You can see in the following image the side-by-side representation of a typical 7 Segment Display and it Segment names. It is technically an 8 Segment Display with 7 Segments responsible for displaying the main numerical data and one dot segment. Most 7 Segment Display have an additional segment in the form of a dot.

The name ‘7 Segment Display’ means that it has 7 LEDs in the form of hexagonal bars that are arranged in the form of ‘8’.Įach LED is known as a ‘Segment’ with names A, B, C, D, E, F and G. A 7 Segment Display is one of the simplest types of display devices that can display numbers from 0 through 9 (you can also display characters from ‘A’ through ‘F’).

Common anode seven segment display